The division of a continuum of stimuli into categories is a fundamental process in several sensory modalities. Categorical perception, which involves both category labeling and discrimination, has been researched extensively at the behavioral level in humans, especially in the context of speech perception. The research proposed here would develop a mouse model to study the neural coding of a categorical percept in the auditory system. Adult mice experienced with pups categorically perceive narrow bandwidth (less than 22.5 kHz) ultrasound noise signals near a 50 kHz center frequency as pup isolation calls, prompting a search and retrieval for lost mouse pups. On the other hand, adult mice that do not have experience with pups do not categorically perceive ultrasounds. The neural correlate of the categorical percept will be studied by performing acute electrophysiology experiments in the auditory cortex of mice that have experience with pups. Aim 1 establishes how natural pup calls are coded in the different auditory cortical subfields, and which subfields are best adapted to the characteristics of natural calls. Aim 2 searches for a possible neural correlate of the categorical perception as a function of bandwidth, and Aim 3 would confirm this by contrasting the neural coding in mice experienced with pups to those who are not. By completing these initial studies, a foundation will be laid for future work into the neuroendocrine and Lneuromodulato mechanisms underlying the formation of the categorical percept using genetic methods.